Quinolonecarboxylic acid derivatives are widely used for medical purpose as a synthetic antibacterial agent. However, emergence of resistant bacteria represented by MRSA has become a major obstacle in such treatment. The quinolonecarboxylic acid derivative represented by formula (1′):
not only exhibits excellent effects on MRSA but also exhibits an antibacterial activity against resistant gram-positive bacteria, and thus is a compound which can solve problems associated with various resistant bacteria. As a process for producing the compound is known a process shown by the following reaction scheme (for example, see Patent Document 1):
Patent Document 1: International Publication WO 02/040478 gazette